1. Field of the Invention
The present disclosure relates to an apparatus and method for making the apparatus used to determine the density of a high pressure fluid. More particularly, the present disclosure is directed to a high pressure vibrating-tube densitometer and a method for making a high pressure vibrating tube densitometer, the densitometer operable at fluid pressures greater than 1500 psi.
2. Background of the Invention
A natural resource such as oil or gas residing in a subterranean formation can be recovered by drilling a well into the formation. The subterranean formation is usually isolated from other formations using a technique known as well cementing. In particular, a wellbore is typically drilled down to the subterranean formation while circulating a drilling fluid through the wellbore. After the drilling is terminated, a string of pipe, e.g., casing, is run in the wellbore. Primary cementing is then usually performed whereby a cement slurry is pumped down through the string of pipe and into the annulus between the string of pipe and the walls of the wellbore to allow the cement slurry to set into an impermeable cement column and thereby seal the annulus. Subsequent secondary cementing operations, i.e., any cementing operation after the primary cementing operation, may also be performed. Examples of secondary cementing operations include squeeze cementing whereby a cement slurry is forced under pressure to areas of lost integrity in the annulus to seal off those areas, and the setting of temporary or permanent cement plugs in order to seal off a desired region of the wellbore.
The well extends through various zones in the earth that the drilling crew may wish to tap. To tap a certain zone, a portion of the casing in the desired zone is fractured. Once the casing is fractured, a fracture fluid is pumped into the fracture to keep it open. The fracture fluid holds the fracture open while still being permeable. Oil and gas is thus able to flow through the fracture and into the wellbore.
In many instances, it is desirable to know the density of the cement or the density of the fracturing fluid in such oil field operations. Conventionally, this is accomplished with the use of nuclear densitometers. However, although these radioactive sensors provide an accurate and compact means of measuring fluid density, there are many problems associated with the use of these nuclear densitometers, and in this time of increasing security, these problems have been escalating recently.
One problem associated with nuclear densitometers is that interstate and international transport of nuclear densitometers can be a difficult process due to the numerous and severe laws and regulations regarding nuclear technology. Another concern is the safe handling and transport of nuclear densitometers. Further, the operators of nuclear densitometers have to be certified or licensed by the proper regulating agency. These health and safety issues, shipping difficulties, and record-keeping burdens motivate development of non-radioactive alternatives for fluid density determination.
Accordingly, an ongoing need exists for a non-radioactive apparatus, and a method for making this apparatus, for determining the density of a fluid at high pressures, such as those encountered in the oil field. In particular, there is a need for such a non-radioactive apparatus and a method for making same, wherein the apparatus can be operated at pressures above 1500 psi. This apparatus, in addition to a high working pressure rating, will preferably also have a high pressure proof rating, provide strong resonance, exhibit limited sensitivity to the stiffness and the loading of the adjacent manifolding, and be compact, lightweight, and erosion-resistant.